KR20120040540A - Light emitting device - Google Patents

Abstract

PURPOSE: A light emitting device is provided to enhance luminous efficiency by including first and second metal layers blocking a current. CONSTITUTION: A first conductive semiconductor layer is arranged on a substrate and includes an aperture plane. An active layer is arranged on the first conductive semiconductor layer. A second conductive semiconductor layer(140) is arranged on the active layer. A first electrode is arranged on the aperture plane of the first conductive semiconductor layer. A second metal layer(160) is arranged on the second conductive semiconductor layer. A light transmissive electrode layer(150) is arranged on the second conductive semiconductor layer while exposing a partial area of the second metal layer.

Description

Light emitting device

Embodiments are directed to a light emitting device having a metal layer that blocks current.

LED (Light Emitting Diode) is a device that converts an electric signal into infrared, visible light or light by using the characteristics of compound semiconductor.It is used in home appliances, remote controls, electronic signs, indicators, and various automation devices. Increasingly, the usage area is expanding.

On the other hand, the external quantum efficiency, which is the light efficiency of the light emitting device, is determined by the product of the internal quantum efficiency and the light extraction efficiency, and the internal quantum efficiency is determined by the quality of the semiconductor and the efficiency of current injection. The light extraction efficiency is reduced by total internal reflection due to the difference in refractive index between gallium nitride (GaN) and air in the light emitting device. In order to increase light extraction efficiency, a vertical light emitting device has been developed, a method of forming surface irregularities, a method of using a reflecting plate, and the like have been developed.

A current blocking layer (CBL) may be provided to prevent current from flowing only in part of the semiconductor layer. However, the existing current limiting layer is composed of silicon dioxide (SiO 2), which causes a problem in coupling with the transparent electrode layer.

In addition, in the case of using PECVD, which is a method of forming a film made of silicon dioxide (SiO 2), there is a problem in that hydrogen is contained and the reliability of the device is lowered.

Accordingly, it is an object of the present invention to provide a light emitting device comprising a metal layer that blocks current.

A light emitting device according to an embodiment of the present invention for solving the above problems, a substrate, a first conductive semiconductor layer disposed on the substrate and having an opening surface, an active layer disposed on the first conductive semiconductor layer, and an active layer A second conductive semiconductor layer disposed on the first conductive layer, a first electrode disposed on the opening surface of the first conductive semiconductor layer, a second metal layer disposed on the second conductive semiconductor layer, and a partial region on the second metal layer. In addition, the light-transmitting electrode layer disposed on the second conductive semiconductor layer, and a second electrode having an area equal to the area of the second metal layer or less than the area of the second metal layer and disposed in contact with the exposed second metal layer.

According to the embodiment, the first and second metal layers using a predetermined metal having a lower work function than pGaN are used for pGaN and nGaN, thereby forming a series diode in the relationship between the pGaN and the second metal layer, thereby forming a predetermined metal in the P-type electrode. By preventing the flow of current to the portion, and serves as a current blocking layer (CBL: Current Blocking Layer), there is an advantage that can overcome the process problems when combined with the transparent electrode.

When the transparent electrode is combined with a current limiting layer made of an insulating material such as silicon dioxide (SiO 2), there is a problem that the film is broken due to a stress problem, but by combining a second metal layer composed of a metal to block the current, When combined, problems with process defects can be solved.

In addition, the existing current limiting layer made of silicon dioxide (SiO 2) formed by PECVD has a problem in device reliability due to the hydrogen contained in the process, and thus has a second metal layer made of a predetermined metal to solve this problem. Can be.

In addition, by providing the first and second metal layer made of a predetermined metal, the generated light is reflected on the first and second metal layer, there is an advantage that the luminous efficiency can be improved.

FIG. 1A is a cross-sectional view of a light emitting device according to an embodiment, and FIG. 1B is a plan view of the light emitting device shown in FIG.
2 is a diagram illustrating a current flow in a translucent semiconductor layer according to an embodiment.
3 is a diagram illustrating a light reflection process according to an embodiment.
4 is a diagram illustrating a bonding process of a predetermined metal and a second conductive semiconductor layer.
5 (a) to 5 (c) are diagrams showing energy levels and heights of energy barriers when voltage is applied.

In the description of embodiments, each layer, region, pattern, or structure is “under” a substrate, each layer (film), region, pad, or “on” of a pattern or other structure. In the case of being described as being formed on the upper or lower, the "on", "under", upper, and lower are "direct" "directly" or "indirectly" through other layers or structures.

In the drawings, the thickness or size of each layer is exaggerated, omitted, or schematically illustrated for convenience and clarity of description. Also, the size of the component does not fully reflect its actual size.

Hereinafter, embodiments will be described in more detail with reference to FIGS. 1 to 5.

1 (a) is a cross-sectional view showing a cross-section of the light emitting device according to the embodiment, Figure 1 (b) is a plan view of the light emitting device shown in Figure 1 (a).

First, referring to FIG. 1A, the light emitting device 100 includes a substrate 110, a first conductive semiconductor layer 120, a first electrode 122, an active layer 130, and a second conductive semiconductor layer ( 140, a second electrode 142, a transparent electrode layer 150, a second metal layer 160, and a first metal layer 170.

The substrate 110 may be a heterogeneous substrate different from a semiconductor layer such as sapphire (Al ₂ O ₃ ) or a homogeneous substrate such as GaN, and may be formed of ZnO, Si, GaP, InP, and GaAs. Can be selected from. In addition, the SiC substrate may have a higher thermal conductivity than the sapphire (Al ₂ O ₃ ) substrate, but is not limited thereto. In addition, an uneven pattern may be formed on an upper surface of the substrate 110.

Although not shown, a layer or pattern using a compound semiconductor of Group 2 to 6 elements on the substrate 110 may be, for example, at least one of a ZnO layer (not shown), a buffer layer (not shown), and an undoped semiconductor layer (not shown). Layers can be formed. The buffer layer or the undoped semiconductor layer may be formed using a compound semiconductor of group III-V group elements, and the buffer layer may reduce the difference in lattice constant with the substrate, and the undoped semiconductor layer may not be doped. It may be formed of a GaN-based semiconductor.

Both the buffer layer (not shown) and the undoped semiconductor layer may be formed on the substrate 110, or may be formed in a structure in which only one layer is formed or both layers are removed, but is not limited thereto. .

The first conductive semiconductor layer 120 may be implemented as an n-type semiconductor layer, and may provide electrons to the active layer 130. The first conductive semiconductor layer 120 may be formed of only an n-type semiconductor layer or may further include an undoped semiconductor layer (not shown) under the n-type semiconductor layer, but is not limited thereto.

For example, the n-type semiconductor layer is a semiconductor material having a compositional formula of In _x Al _y Ga _{1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1), for example For example, it may be selected from GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, and the like, and an n-type dopant such as Si, Ge, Sn, or the like may be doped.

The undoped semiconductor layer (not shown) is a layer formed for improving the crystallinity of the n-type semiconductor layer, except that the n-type dopant is not doped and has a lower electrical conductivity than the n-type semiconductor layer. Is the same as

For example, NH3 and trimetal gallium (TMGa) are supplied onto a buffer layer (not shown) to form an undoped semiconductor layer with a predetermined thickness.

Both the buffer layer (not shown) and the undoped semiconductor layer (not shown) may be formed on the substrate 110, or may be formed in a structure in which only one layer is formed or both layers are removed. It is not limited to.

Meanwhile, the first conductive semiconductor layer 120 may be formed by supplying a silene (SiH ₄ ) gas including n-type dopants such as NH ₃ , TMGa, and Si, and may be formed as a multilayer film, and the clad layer may further be formed. May be included.

In addition, the active layer 130 may be formed on the first conductive semiconductor layer 120. The active layer 130 is a region where electrons and holes are recombined. The active layer 130 transitions to a low energy level as the electrons and holes recombine, and may generate light having a corresponding wavelength.

The active layer 130 is, for example, including a semiconductor material having a compositional formula of _{In x Al y Ga 1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) It may be formed, and may be formed of a single quantum well structure or a multi quantum well structure (MQW). In addition, a quantum wire structure or a quantum dot structure may be included.

A second conductive semiconductor layer 140 and injects holes to the above-mentioned active layer _{(130), In x Al y} Ga 1 -x- y N (0≤x≤1, 0≤y≤1, 0≤x + y A semiconductor material having a compositional formula of ≦ 1), for example, GaN, AlN, AlGaN, InGaN, InN, InAlGaN, AlInN, and the like, and may be doped with p-type dopants such as Mg, Zn, Ca, Sr, and Ba. have.

The light emitting structure layer 180 may include an N-type semiconductor layer or a P-type semiconductor layer on the second conductive semiconductor layer 140. Accordingly, the light emitting structure layer 180 may include at least one of a P-N junction, an N-P junction, a P-N-P junction, and an N-P-N junction structure.

In the embodiment, the light emitting structure layer 180 includes an n-type nitride semiconductor layer including an n-type dopant, an active layer formed on the n-type nitride semiconductor layer, and a p-type nitride semiconductor layer including a p-type dopant on the active layer. Although the description has been made with reference to, the present invention is not limited thereto, and the laminated structure and material of the light emitting structure layer 180 may be variously modified.

For example, the first conductive semiconductor layer 120, the active layer 130, and the second conductive semiconductor layer 140 may include, for example, metal organic chemical vapor deposition (MOCVD) and chemical vapor deposition (CVD). Deposition), Plasma-Enhanced Chemical Vapor Deposition (PECVD), Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), and the like. It is not limited thereto.

A portion of the active layer 130 and the second conductive semiconductor layer 140 are removed to expose a portion of the first conductive semiconductor layer 120, and titanium or the like is disposed on the exposed upper surface of the first conductive semiconductor layer 120. The first electrode 122 may be formed.

The first metal layer 170 made of a predetermined metal is positioned between the first conductive semiconductor layer 120 and the first electrode 122. Preferably, the first metal layer 170 may be made of aluminum (Al) or aluminum (Al) alloy. The first metal layer 170 may form an ohmic contact with the first conductive semiconductor layer 120. As the first metal layer 170 is positioned on a portion of the first conductive semiconductor layer 120, light emitted from the active layer 130 is directed to the first electrode 122 formed on the first metal layer 170. Can be prevented from being absorbed. That is, the first metal layer 170 may reflect light absorbed by the first electrode 122 to increase the light extraction efficiency of the light emitting device.

In addition, although the third conductive semiconductor layer (not shown) including the n-type semiconductor layer or the p-type semiconductor layer may be formed on the second conductive semiconductor layer 140, the second conductivity is different from the second electrode 142. The semiconductor layer 140 is connected. In addition, the doping concentrations of the dopants in the first conductive semiconductor layer 120 and the second conductive semiconductor layer 140 may be uniformly or non-uniformly formed. That is, the structure of the plurality of semiconductor layers may be variously formed, but is not limited thereto.

In addition, the transparent electrode layer 150 may be formed on the second conductive semiconductor layer 140, and a second electrode 142 made of nickel (Ni) may be formed on an outer surface of the transparent electrode layer 150.

Concave-convex to improve light extraction efficiency may be formed in a portion or the entire region of the transparent electrode layer 150 or the surface of the second conductive semiconductor layer 140 where the second electrode 142 is not formed by a predetermined etching method. have. The second electrode 142 may be formed on a flat surface where the unevenness is not formed, or may be formed on the upper surface where the unevenness is formed, but is not limited thereto.

The second metal layer 160 may be formed on a portion of the second conductive semiconductor layer 140 so that at least a portion thereof corresponds to the position of the second electrode 142. The second metal layer 160 may be formed of a predetermined metal, and may preferably include aluminum (Al) or aluminum (Al) alloy. The second metal layer 160 is not limited thereto, and the work function of the predetermined metal constituting the second metal layer 160 is greater than the work function of the constituent materials of the second conductive semiconductor layer 140 described above. It may include small metals.

The work function is conceptually the energy required to export the electrons inside the device into the vacuum. The energy level is the difference between the energy level in the vacuum and the Fermi Energy Level. The work function of the semiconductor depends on the doped dopant.

That is, according to the amount or type of the doped dopant, the size of the energy barrier (Energy Barrier) in the coupling with the second metal layer 160 may vary.

According to an embodiment, the Fermi energy level of aluminum (Al) is lower than the Fermi level of the first conductive semiconductor layer 120 and higher than the Fermi level of the second conductive semiconductor layer 140. Therefore, when aluminum (Al) is in contact with the p-type semiconductor, the work function of the p-type semiconductor constituting the second conductive semiconductor layer 140 is greater. When the work function of the p-type semiconductor is large, the energy of electrons in aluminum (Al) is greater, so that the energy of electrons in aluminum (Al) moves to the p-type semiconductor, resulting in a depletion layer. Fermi Energy Level is the energy level of a home appliance at 0K absolute.

The work function of aluminum (Al) or aluminum (Al) alloy is smaller than that of the p-type semiconductor and larger than that of the n-type semiconductor. In the case of the second metal layer 160 or the first metal layer 170 made of aluminum (Al) or aluminum (Al) alloy, the second metal layer 160 and the second conductive semiconductor layer 140 make Schottky contact. Since the work function of the p-type semiconductor constituting the second conductive semiconductor layer 140 is larger than that of aluminum (Al) or aluminum (Al) alloy, electrons are transferred from the second metal layer 160 to the second conductive semiconductor layer 140. Move and a current flows from the second conductive semiconductor layer 140 to the second metal layer 160.

As the Schottky contact is formed, when a positive voltage is applied to the second metal layer 160, no current flows from the second metal layer 160 toward the second conductive semiconductor layer 140.

Meanwhile, in the case of the first metal layer 170, an ohmic contact is made with the first conductive semiconductor layer 120, so that electrons move from the first metal layer 170 to the first conductive semiconductor layer 120, and the current is first. 1, the conductive semiconductor layer 120 flows in the direction of the first metal layer 170.

The transparent electrode layer 150 includes ITO, IZO (In-ZnO), GZO (Ga-ZnO), AZO (Al-ZnO), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO), IrOx, RuOx, RuOx At least one of / ITO, Ni / IrOx / Au, and Ni / IrOx / Au / ITO may be formed and formed on the entire outer surface of the second conductive semiconductor layer 140 to prevent current grouping. have.

The second metal layer 160 may be disposed on a portion of the second conductive semiconductor layer 140, and the light transmissive electrode layer 150 may be formed on the second conductive semiconductor layer while exposing a portion of the upper surface of the second metal layer 160. .

In addition, the second electrode 142 may be disposed to contact at least a portion of the upper surface of the exposed second metal layer 160. The area of the second metal layer 160 may be equal to the area of the second electrode 142 or larger than the area of the second electrode 142. When a bias is applied to the second electrode 142, since a current flows, the second metal layer 160 having an area equal to or larger than that of the second electrode 142 is provided through the second electrode 142. It is possible to prevent the grouping phenomenon in which electrons are concentrated only on the lower portion of the second electrode 142.

The metal constituting the second metal layer 160 has a work function smaller than that of the p-type semiconductor, which is a constituent material of the second conductive semiconductor layer 140. Preferably, the metal constituting the second metal layer 160 may be aluminum (Al) or aluminum (Al) alloy.

The above-described aluminum (Al) or aluminum (Al) alloy is an example of a metal constituting the second metal layer 160 and the first metal layer 170, but is not limited thereto.

That is, the Fermi Energy Level of the metal constituting the second metal layer 160 is higher than the Fermi Energy Level of the p-type semiconductor.

On the other hand, the second metal layer 160 and the second conductive semiconductor layer 140 make a rectifying contact (Schottky Contact), the electrons from the second metal layer 160 to the second conductive semiconductor layer 140. As it moves, current flows from the second conductive semiconductor layer 140 to the second metal layer 160.

That is, when a positive voltage is applied to the second conductive semiconductor layer 140, a series diode form through which a current flows may be formed. According to the embodiment, when a positive voltage is applied to the second electrode 142 positioned on the second metal layer 160, the second metal layer 160 is reversed in the direction of the second conductive semiconductor layer 140. A bias is applied, so that little current flows.

Since the existing second metal layer 160 is made of silicon dioxide (SiO 2), there is a problem such as cracking of the film due to the light-transmitting electrode layer 150 and a stress problem.

In addition, the existing second metal layer 160 made of silicon dioxide (SiO 2) is formed through a plasma enhanced CVD (PECVD) process. PECVD process can deposit silicon dioxide film at low temperature, but process variables such as substrate temperature, gas composition ratio, gas flow rate, pressure, input power, high frequency, electrode spacing, etc. must be controlled. Since it is present in the plasma, there is a problem in that hydrogen is contained, which is vulnerable to device reliability.

The first metal layer 170 is positioned between the first conductive semiconductor layer 120 and the first electrode 122, and is formed to be the same as the area of the first electrode 122 or larger than the area of the first electrode 122. Can be. When a bias is applied to the first electrode 122, a current flows, so that light is transmitted to the first electrode 122 by providing a first metal layer 170 having an area equal to or larger than that of the first electrode 122. Can be absorbed. That is, the first metal layer 170 reflects light.

The metal constituting the first metal layer 170 has a work function larger than that of the n-type semiconductor, which is a constituent material of the first conductive semiconductor layer 120. Preferably, the metal constituting the first metal layer 170 may be aluminum (Al) or aluminum (Al) alloy.

That is, the Fermi Energy Level of the metal constituting the first metal layer 170 is lower than the Fermi Energy Level of the n-type semiconductor.

Meanwhile, the first metal layer 170 and the first conductive semiconductor layer 120 make ohmic contacts. The n + type semiconductor layer may further include an ohmic contact between the first conductive semiconductor layer 120 and the first metal layer 170.

When the metals constituting the first metal layer 170 and the second metal layer 160 are the same, for Schottky contact with the second conductive semiconductor layer 140 and ohmic contact with the first conductive semiconductor layer 120, The degree of aluminum (Al) alloy may vary. In addition, heat treatment may be performed for efficient ohmic contact and schottky contact.

In addition, first and second passivation layers 162 and 172 may be further provided outside the second metal layer 160 and the first metal layer 170 to prevent diffusion of aluminum (Al) or mixing of other materials. can do. The first and second passivation layers 162 and 172 (Capping Metal) include titanium (Ti), nickel (Ni), chromium (Cr), tungsten (W), molybdenum (Mo), niobium (Nb), and rudenium (Ru). ), Rh (rhodium), palladium (Pd), platinum (Pt), iridium (Ir), gold (Au), titanium nitride (TiN), titanium-tungsten (TiW) and the like may be included.

FIG. 1B is a plan view of the light emitting diode illustrated in FIG. 1A. The first metal layer 170 and the first electrode 122 are positioned on the first conductive semiconductor layer 120, and the first electrode 122 is positioned on the first conductive semiconductor layer 120. An area of the metal layer 170 may be equal to or larger than that of the first electrode 122.

The second metal layer 160 and the second electrode 142 are positioned on the transparent electrode layer 150, and the area of the second metal layer 160 may be equal to or larger than the area of the second electrode 142. .

FIG. 2 is a diagram showing a flow of current in the translucent semiconductor layer according to the embodiment. FIG.

The movement of the current in the second electrode 142 may be evenly distributed in the light transmitting electrode layer according to the presence of the second metal layer 160. That is, due to the presence of the second metal layer 160 serving as a current blocking layer (CBL), it is possible to prevent clustering of electrons provided through the second electrode 142 to be concentrated only under the second electrode 142. Can be.

The second metal layer 160 may be made of a predetermined metal, and preferably, may be made of aluminum (Al) or aluminum (Al) alloy. The process of blocking most of the current through the second metal layer 160 is as described above with reference to FIG. 1.

3 is a diagram illustrating a light reflection process according to an embodiment.

The second metal layer 160 may be formed of a predetermined metal to block the flow of current and to prevent light from being absorbed by the second electrode 142, thereby improving light extraction efficiency.

In addition, the reflective layer 310 is positioned on the substrate 110, and when the light generated from the active layer 130 is emitted toward the substrate 110, the reflective layer 310 may be reflected to increase the light extraction efficiency.

The reflective layer 310 is made of at least one of silver (Ag), aluminum (Al), lead (Pb), and rhodium (Rh) or an alloy thereof to reflect light moving toward the substrate 110. Therefore, the light emitting efficiency of the light emitting device 100 that emits light through the light emitting structure layer 180 may be increased.

4 is a diagram illustrating a bonding process of a predetermined metal and a second conductive semiconductor layer.

As shown, when the predetermined metal constituting the second metal layer 160 and the p-type semiconductor constituting the second conductive semiconductor layer 140 exist separately, the Fermi level of the metal is higher than the Fermi level of the p-type semiconductor. It is higher and the work function of the metal is smaller than that of the p-type semiconductor.

When the predetermined metal constituting the second metal layer 160 and the p-type semiconductor constituting the second conductive semiconductor layer 140 are combined, the Fermi levels are equally aligned, and the electrons of the metal move toward the p-type semiconductor side. do.

5 is a diagram illustrating energy levels and heights of energy barriers when voltage is applied.

Referring to FIG. 5 (a), FIG. 5 (a) illustrates a case in which a positive bias voltage (+) is applied to the second conductive semiconductor layer, and FIG. 5 (b) shows a reverse bias on the second conductive semiconductor layer. The case where a phosphorus (-) voltage is applied is shown.

When a positive voltage is applied to the second conductive semiconductor layer 140, the height of the energy barrier decreases, thereby increasing the number of electrons moving from the metal to the second conductive semiconductor layer 140.

Conversely, referring to FIG. 5B, when a positive voltage is applied to aluminum Al, which is one of the embodiments constituting the second metal layer 160, the height of the energy barrier is increased, and the metal is the second conductive semiconductor. The number of electrons moving to layer 140 is reduced.

That is, as shown in FIG. 5C, since a + voltage is applied to the second electrode 142 positioned on the second metal layer 160, the voltage is applied to aluminum Al forming the second metal layer 160. Is applied to form the same as in FIG. 5 (b), the height of the energy barrier is increased, the number of electrons moving from the metal to the second conductive semiconductor layer 140 decreases, and a current flows through the second metal layer 160. Rarely flows.

The light emitting device 100 according to the embodiment may be mounted in a package, and a plurality of light emitting device packages on which the light emitting devices are mounted are arranged on a substrate, and a light guide plate, a prism sheet, which is an optical member, on an optical path of the light emitting device package, Diffusion sheet or the like may be disposed. The light emitting device package, the substrate, and the optical member may function as a light unit. Another embodiment may be implemented as a display device, an indicator device, or a lighting system including the light emitting device or the light emitting device package described in the above embodiments, and for example, the lighting system may include a lamp or a street lamp.

While the above has been shown and described with respect to preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, it is usually in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

100 light emitting element 110 substrate
120: n-type semiconductor layer 130: active layer
140: p-type semiconductor layer 150: a transparent electrode layer
160: second metal layer 170: first metal layer
180: light emitting structure layer

Claims (12)

Board;
A first conductive semiconductor layer disposed on the substrate and having an opening surface;
An active layer disposed on the first conductive semiconductor layer;
A second conductive semiconductor layer disposed on the active layer;
A first electrode disposed on the opening surface of the first conductive semiconductor layer;
A second metal layer disposed on the second conductive semiconductor layer;
A transmissive electrode layer disposed on the second conductive semiconductor layer while exposing a portion of the region on the second metal layer; and
And a second electrode disposed to be in contact with the exposed second metal layer and having an area equal to or smaller than that of the second metal layer. The method of claim 1,
The first conductive semiconductor layer is an n-type semiconductor layer, the second conductive semiconductor layer is a p-type semiconductor layer. The method of claim 1,
The second metal layer is a light blocking device (CBL: Current Blocking Layer). The method of claim 1,
The work function of the second metal layer is smaller than the work function of the second conductive semiconductor layer. The method of claim 1,
The second metal layer is an Al (aluminum) or Al (aluminum) alloy. The method of claim 1,
The light emitting device further comprising a first metal layer having the same material as the second metal layer below the first electrode. The method of claim 6,
And the first metal layer is in ohmic contact with the first conductive semiconductor layer. The method of claim 1,
The second metal layer is,
A light emitting device in schottky contact with the second conductive semiconductor layer. The method of claim 1,
A light emitting device comprising a first protective film on the outside of the second metal layer. The method of claim 1,
A light emitting device comprising a second protective film on the outside of the first metal layer. The method according to claim 9, wherein
The first protective layer and the second protective layer may include titanium (Ti), nickel (Ni), chromium (Cr), tungsten (W), molybdenum (Mo), niobium (Nb), ruthenium (Ru), rhodium (Rh), A light emitting device comprising at least one of Pd (palladium), platinum (Pt), Ir (iridium), gold (Au), titanium nitride (TiN) and titanium-tungsten (TiW). The method of claim 1,
The translucent electrode layer is formed of ITO, IZO (In-ZnO), GZO (Ga-ZnO), AZO (Al-ZnO), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO), IrOx, RuOx, RuOx / A light emitting device comprising at least one of ITO, Ni / IrOx / Au, and Ni / IrOx / Au / ITO.

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